The Role of Policy in Prison Growth and Decline

Between 1975 and 2008, the US incarceration rate increased by roughly 400 percent. Trends in crime rates, arrest rates per crime committed, conviction rates per arrest, and expected time-served in prison given conviction all influence trends in incarceration rates. Available data do not allow researchers to precisely measure the contribution of each of these factors to the US prison boom. However, increases in expected prison time-served among those arrested for many different offenses were the most important drivers of rising incarceration rates. We argue that changes in policies that govern sentencing and parole are the likely drivers of these increases. We also discuss potential reforms that may reduce expected time-served among convicted offenders while minimizing harm to public safety.